As electronic devices having a plurality of electrical components, a color thermal printer and a color laser printer, for example, are known. In a color thermal printer disclosed in JP-A-2005-109025, an image formed of three colors is thermally recorded by heating each thermal coloring layer of a color thermosensitive recording paper sheet with a thermal head. The sheet on which the image of each color is thermally recorded is sent to an optical fixing unit. The image is fixed by applying a fixing light over the entire recording face of the color thermosensitive recording paper sheet so that the thermal coloring on the upper layer may not be effected at the time of thermally recording on the lower layer for thermal coloring. The optical fixing unit includes groups each composed of a plurality of yellow light emitting elements and groups each composed of a plurality of magenta light emitting elements. One light emitting element for display is connected in series with light emitting elements in each group. A drive power source is connected in parallel with the groups to supply power and constitutes an LED drive circuit for driving the light emitting elements.
In the color thermal printer as disclosed in JP-A-2005-109025, for example, when any one of magenda light emitting elements in a group does not fail due to disconnection, a current flows through the light emitting element for display provided in the group to turn on the light emitting element for display. When one of magenta light emitting elements fails due to disconnection, no current flows through the light emitting element for display and thus the light emitting element for display is turned off. Therefore, the group including faulty light emitting elements can be specified and repaired by turning on or off the light emitting element for display.